The present invention relates generally to a system for delivering medicine to a patient, and more particularly, to a system having in combination a spring-driven infusion pump and a bolus injector, which enable a user to selectively deliver a predetermined dosage of a fluid medication to a treatment site either automatically at a moderate flow rate over a long time or manually at a higher flow rate over a short time.
Pain management is an important aspect of post-operative recovery from surgery. Pain management usually begins immediately following the surgical procedure with the administration of narcotics or other pain control medications to the patient while the patient is under the direct supervision of the health care provider. The pain control medications are most commonly administered either orally or by injection.
The proliferation of less-invasive arthroscopic techniques for the surgical repair of many joint or soft tissue injuries and ailments has significantly reduced post-operative recovery times and the attendant pain experienced by the patient. The current trend toward arthroscopic techniques frequently enables surgical procedures to be performed on an outpatient basis or with shortened post-operative hospital stays.
As a result, the bulk of the post-operative recovery time is spent in the home or even in the workplace. One goal of home recovery is to phase the patient back into routine physical activities relatively quickly as a means of shortening the post-operative recovery time.
Since the patient is generally not under the direct supervision of the health care provider when in the home or workplace, the responsibility for administering pain control medications falls on the patient in these environments. The vast majority of self-administered pain control medications are oral medications because most individuals lack the requisite knowledge, skill, and experience to self-administer pain control medications by injection. Unfortunately, however, pain control medications administered orally are transported throughout the body and correspondingly affect the entire body, often causing undesirable side effects such as drowsiness, disorientation, nausea, constipation or vomiting. In contrast, injected pain control medications can be administered more locally than orally administered medications, thereby frequently avoiding the undesirable side effects of oral medications. In addition, injected pain control medications reach the treatment site more rapidly and in greater concentrations than oral medications, rendering injected pain control medications a more effective pain control therapy.
To exploit the advantages of injected pain care medications, devices have been developed to inject the pain care medication into the treatment site in an automated manner, which requires minimal patient intervention. Such devices typically meter the pain care medication to the treatment site continuously over a long period of time. Automated continuous injection devices are, nevertheless, not entirely satisfactory. It has been found in many instances that pain care medication is most effective if periodically injected into the treatment site as a single relatively large bolus dosage whenever the patient senses the need rather than continuously injecting the same overall dosage of medication into the treatment site over a relatively long period of time. However, if the patient is allowed to self-administer injection of the pain care medication on an as needed basis in the absence of supervision of a health care provider, the risk of overmedication is significant.
The present invention recognizes a need for a fluid injection device, which selectively enables effective auto-administration of a fluid medication or, in the alternative, effective self-administration of the fluid medication by a patient while diminishing the risk of overmedication, even when the patient lacks the requisite knowledge, skill or experience to perform injections. Accordingly, it is an object of the present invention to provide a medication delivery system, wherein operation of the system is selective between an automated or extended mode and a manual or instantaneous mode. More particularly, it is an object of the present invention to provide such a medication delivery system, wherein the patient elects extended injection of a predetermined dosage of a fluid medication into a treatment site at a moderate flow rate over a long time or, in the alternative, elects to effect instantaneous injection of the predetermined dosage of the fluid medication into the treatment site at a higher flow rate over a short time. It is another object of the present invention to provide such a medication delivery system, wherein the system can effectively reduce the risk of overmedication even when the patient operates the system in the manual or instantaneous mode. It is still another object of the present invention to provide such a medication delivery system, wherein the system can be effectively monitored and operated by a patient lacking any specific medical knowledge, skill or experience in performing injections. It is yet another object of the present invention to provide such a medication delivery system, which is fully portable while operating so that the system can be used by the patient during normal daily activity.
These objects and others are accomplished in accordance with the invention described hereafter.
A first embodiment of the present invention is a medical infusion pump comprising a fluid storage chamber, a pump outlet, and a pump flowpath positioned between the fluid storage chamber and the pump outlet to provide fluid communication therebetween. The pump flowpath includes a flow restriction, a drip chamber, an outlet tube and a sight window. The flow restriction exits into the drip chamber and the sight window is oriented to enable visual contact with the drip chamber. The flow restriction is sized to convert a continuous stream of fluid entering the flow restriction from the fluid storage chamber to a drip stream exiting the flow restriction into the drip chamber. The outlet tube is positioned beneath the flow restriction in the drip chamber and separated from the flow restriction by a drip gap. The outlet tube is configured to revert the drip stream exiting the flow restriction to a reverted continuous stream. The infusion pump further comprises a displacement piston displacably positioned in the fluid storage chamber and an elastic member engaging the displacement piston and transitionable between a more stressed position and a less stressed position to displace the displacement piston. The elastic member is preferably a coil spring.
Another embodiment of the present invention is a medication delivery system comprising an infusion pump and a bolus injector. The infusion pump includes a fluid storage chamber, a pump outlet, a pump flowpath providing fluid communication between the fluid storage chamber and the pump outlet, a displacement piston displacably positioned in the fluid storage chamber, and an elastic member engaging the displacement piston and transitionable between a more stressed position and a less stressed position to displace the displacement piston. The bolus injector is positioned in series with the infusion pump and is a flexible bladder enclosing a bolus chamber. The bolus chamber has a fluid capacity substantially less than the fluid storage chamber. The bladder may have an elastic memory to restore the bladder to an initial configuration after the bladder is deformed by compression. The bolus injector has an injector inlet into the bolus chamber and an injector outlet out of the bolus chamber. The injector inlet is connected to the pump outlet. The pump flowpath may include a flow restriction, drip chamber, outlet tube and sight window substantially as recited above.
A further embodiment of the present invention is a medication delivery system comprising a first infusion pump, a second infusion pump, a bolus injector, a junction and a common flow tube. The first infusion pump includes a first fluid storage chamber, a first pump outlet, a first pump flowpath providing fluid communication between the first fluid storage chamber and the first pump outlet, a first displacement piston displacably positioned in the first fluid storage chamber, and a first elastic member engaging the first displacement piston and transitionable between a more stressed position and a less stressed position to displace the first displacement piston. The second infusion pump similarly includes a second fluid storage chamber, a second pump outlet, a second pump flowpath providing fluid communication between the second fluid storage chamber and the second pump outlet, a second displacement piston displacably positioned in the second fluid storage chamber, and a second elastic member engaging the second displacement piston and transitionable between a more stressed position and a less stressed position to displace the second displacement piston. The bolus injector is positioned in series with the second infusion pump and is substantially as recited above. The second pump outlet is connected to the injector inlet and the junction connects the first pump outlet with the injector outlet. The common flow tube exits the junction and is in fluid communication with the first pump outlet and the injector outlet. The first pump flowpath may include a flow restriction, drip chamber, outlet tube and sight window substantially as recited above.
Yet another embodiment of the present invention is a medication delivery system comprising an infusion pump, a bolus injector, a junction and a common flow tube. The infusion pump includes a fluid storage chamber, a first pump outlet and a second pump outlet, a pump flowpath providing fluid communication between the fluid storage chamber and the first pump outlet, a displacement piston displacably positioned in the fluid storage chamber, and a elastic member engaging the displacement piston and transitionable between a more stressed position and a less stressed position to displace the displacement piston. The bolus injector is substantially as recited above. The second pump outlet is connected to the injector inlet and the junction connects the first pump outlet with the injector outlet. The common flow tube exits the junction and is in fluid communication with the first pump outlet and the injector outlet. The first pump flowpath may include a flow restriction, drip chamber, outlet tube and sight window substantially as recited above.
Still another embodiment of the present invention is a method for delivering a fluid medication to a treatment site of a patient. A bolus injector is charged with a fluid medication. The bolus injector is a flexible bladder enclosing a bolus chamber and having an injector inlet into the bolus chamber and an injector outlet out of the bolus chamber. A fluid storage chamber serially positioned upstream of the bolus injector is also charged with the fluid medication. The fluid storage chamber is in fluid communication with a pump outlet via a pump flowpath and the pump outlet is in fluid communication with the injector inlet. A displacement force is applied to the fluid medication in the fluid storage chamber from an elastic member transitioning from a more stressed position to a less stressed position. The displacement force serially displaces the fluid medication from the fluid storage chamber and the pump flowpath into the bolus chamber. An outlet valve positioned at the injector outlet which is biased closed is opened in response to the ambient pressure of the fluid medication contacting the outlet valve to discharge the fluid medication from the injector outlet. The method may further comprise connecting the injector outlet with an inlet end of a catheter, positioning an outlet end of the catheter in a treatment site of a patient, and displacing the fluid medication through the catheter to deliver the fluid medication to the treatment site.
In accordance with specific aspects of the present embodiment, the bolus injector is charged with the fluid medication by displacing the fluid medication from the pump flowpath into the bolus chamber. Alternatively, the bolus injector is charged with the fluid medication by injecting the fluid medication into the bolus chamber from a source downstream of the infusion pump. In accordance with another specific aspect of the present invention, the fluid medication is preferably displaced from the fluid storage chamber as a continuous stream. The continuous stream of the fluid medication is then driven into a flow restriction in the pump flowpath and the fluid medication exits the flow restriction as a drip stream.
Another embodiment of the present invention is a method for delivering a fluid medication to a treatment site of a patient, which comprises charging a bolus injector and a fluid storage chamber serially positioned upstream of the bolus injector with a fluid medication substantially as described above. The practitioner then selects between an extended mode and an instantaneous mode of delivering the fluid medication to a treatment site. The extended mode is performed by applying a first displacement force to the fluid medication in the fluid storage chamber from an elastic member transitioning from a more stressed position to a less stressed position. The first displacement force serially displaces the fluid medication from the fluid storage chamber through the pump flowpath, the bolus chamber and the injector outlet into the treatment site at a first flow rate over a long time. The instantaneous mode is performed by applying a second displacement force to the bolus injector sufficient to deform the bolus injector. The second displacement force displaces the fluid medication from the bolus chamber and discharges the fluid medication from the injector outlet into the treatment site at a higher second flow rate over a short time. The method further comprises recharging the bolus injector with the fluid medication after the instantaneous mode of operation by applying the first displacement force to the fluid medication in the fluid storage chamber. The first displacement force serially displaces the fluid medication from the fluid storage chamber through the pump flowpath and injector inlet into the bolus chamber.
In accordance with a specific aspect of the present embodiment, the fluid medication is preferably displaced from the fluid storage chamber as a continuous stream. The continuous stream of the fluid medication is driven into a flow restriction in the pump flowpath and the fluid medication exits the flow restriction as a drip stream.
The present invention will be further understood from the drawings and the following detailed description.